Научный вестник МГТУ ГА (Jan 2017)
NUMERICAL SIMULATION OF CAVITY FLOW AND FLOW OVER AIRCRAFT COMPARTMENT USING SEMI-EMPIRICAL TURBULENCE MODELS
Abstract
The article is devoted to the validation and application of CFD code for turbulent flows. Two-dimensional unsteady flows in the cavities and compartments and three-dimensional flow in the compartment of complex geometry have been considered. Two turbulence parameter oriented models are used.Numerical simulation of unsteady transonic flow (Mоо=0.74) in a narrow channel with a cavity inside has been conducted. The dependence of the static pressure on time at fixed points in space has been obtained. The fast Fourier transform has been applied for processing data of static pressure. The difference of 6-10% between the numerical and experi-mental data has been obtained.The computations of unsteady transonic cavity flow with Mach number Mоо=0.85 have been performed. Low frequency oscillations of the static pressure in several fixed points in space have been obtained. Power spectrum of oscillations at the center of the cavity is compared with experimental data and Rossiter modes. An acceptable agreement between experimental and computed data has been achieved. The influence of geometrical factors on the frequency characteristics of the flow has been investigated. For this purpose two round flaps have been added to the cavity. The most low-frequency oscillation modes changed by the presence of the flaps. The first mode was gone, the second mode amplitude decreased and the third mode amplitude significantly decreased. The changes in height of protruding part of the geometry to the external flow have led to changes in pressure pulsation amplitude without changing the frequency. The spectral functions obtained while using the two considered models of turbulence have been compared for this case. It is found that the frequency values are only slightly different; the main difference is present at the amplitude of pulsations.The effect of deflection of flat flap on the non-stationary subsonic flow parameters in a cylindrical body with an inner compartment has been investigated. The cases of deflection angles of the flap inside the compartment with values 26º and 41º above the horizontal plane, and also the case without flap have been considered. Low-frequency oscillations of the static pressure have been obtained. The presence of the flap did not change the frequency of static pressure pulsations. With the increase of the choke deflection angle, the oscillation amplitude increases at all considered points of the flow too.
